Curvilinear canopies such as those disclosed in U.S. Pat. Nos. 3,461,760 and 4,173,161 are well known in the art of feeding elongate sheets of material in which articles, such as cups or the like, have been vacuum formed to punch out devices where a die is employed to trim the article from the sheet. In the usual case, the canopy is stationary and merely defines a curved path over which the sheet is guided in its transit from the forming machine to the trim press die. In these arrangements, step by step feeding movement of the sheet to advance successive articles into operative relationship with the die is accompanied by feeding fingers which engage projections formed along the edges of the sheet to advance the sheet in step by step movement synchronized with the reciprocatory stroke of the die. See, for example, U.S. Pat. No. 4,173,161.
Because these feeding fingers must, during their feeding stroke, pull a substantial length of the sheet across the stationary canopy, it has been suggested that the canopy itself be capable of being oscillated to accomplish the feeding action. However, prior attempts to provide an oscillating canopy feed have not proven satisfactory, primarily because problems of overtravel or bunching of the plastic sheet on the canopy have been encountered.
The present invention is especially directed to an oscillating canopy employed in the feeding of sheet material from a forming machine to a trim press which is constructed in a manner such that bunching of the material does not occur.